Apparatus and method for analyte detection

ABSTRACT

Disclosed is a testing device and methods for the identification of an analyte of interest in a sample. In a preferred embodiment, the testing device includes a front panel having at least one sample application aperture; a rear panel having at least one solvent application aperture; a sample collection matrix disposed between the rear panel and the front panel, the sample collection matrix being in communication with the sample and solvent application apertures of the front and rear panels; and an insertable test strip containing a reagent enabling detection of the analyte of interest.

BACKGROUND OF THE INVENTION

A variety of diagnostic devices have been developed for the detection ofan analyte of interest in a sample. In those devices in which samplecollection and testing functions are non-linked, the transfer ofcollected sample to testing apparatus introduces a potential source oferror. In those devices in which sample collection and testing functionsare linked, the devices are dedicated in their entirety to the detectionof a particular analyte and are not easily adaptable to a wide range ofanalyte detection. These two limitations associated with prior artdevices are overcome by the invention disclosed herein.

SUMMARY OF THE INVENTION

The present invention relates to a testing device and methods for theidentification of an analyte of interest in a sample. The testing deviceoffers a variety of advantages over prior art devices. An importantfeature of the testing device of the present invention is that thesingle device serves a collection and testing function. However, thetesting function is not linked to collection. That is, the collection ofa sample (e.g., by a patient in their home) and application to thetesting device does not yield a test result. In order to determine thetest result, an insertable testing element must be inserted into thedevice, and the sample must be rehydrated. In practice, the testingelement will not be provided with the device and, therefore, the patientwill not self-diagnose at home.

The issue of self-diagnosis of serious disease such as cancer or AIDShas been considered at length. There is general consensus thatself-diagnosis of such disease states is not preferred. Rather, it isgenerally accepted that a positive diagnosis for such a disease stateshould be communicated by a doctor, together with information relatingto the availability of counselling services.

With respect to mammalian systems (e.g., humans), samples amenable toanalysis using the testing device of the present invention includebiological fluids (e.g., blood, urine, semen, saliva, etc.) orexcrements. Such biological fluids can carry a variety of analytes, thepresence of which can be diagnostic for a particular disease state. Animportant example of a disease state which is characterized by thepresence of a disease-specific analyte in a biological fluid is AcquiredImmunodeficiency Syndrome (AIDS). Using the composition and methods ofthe present invention, the presence of antibodies specific for the HumanImmunodeficiency Virus (HIV), the causative agent of AIDS, in a bloodsample are detectable.

The application of the subject invention to the detection of diseasestates in humans is of primary importance. However, in addition to usein the context of the diagnosis of serious disease states, the device ofthe present invention is also useful in a variety of other contexts.Applications in connection with the analysis of microbes, plants,animals, food and water are all anticipated.

For example, ground water samples can be analyzed for the presence ofcontaminants such as atrazine. Food, such as ground beef, can beanalyzed for the presence of contamination by bacteria such as E. coli.In the plant kingdom, the compositions and methods of the presentinvention can be applied to the analysis of, for example, pollen, sporesand plant vascular fluids. Generally speaking, the only requirement fordetection using the methods and compositions of the present invention isthat the analyte of interest should be soluble or suspendable in anaqueous solution.

The compositions and methods of the present invention are particularlyuseful for the detection of occult gastrointestinal bleeding. Thedetection of occult gastrointestinal bleeding is a common method forscreening for colo-rectal cancer. Commonly referred to as the fecaloccult blood (FOB) test, a variety of formats are known in the art (seee.g., U.S. Pat. Nos. 3,996,006; 4,225,557; 4,789,629; 5,064,766;5,100,619; 5,106,582; 5,171,528; 5,171,529; and 5,182,191).

The majority of test formats are based on the chemical detection of hemegroups present in stool as a breakdown product of blood. In such tests,the pseudoperoxidase nature of the heme group is used to catalyze acolorimetric reaction between an indicator dye and peroxide. The oxygensensitive dye can be gum guaiac, orthodianisidine, tetramethylbenzidine,or the like with guaiac being preferred.

While guaiac-based FOB tests are inexpensive and simple to use, thereare disadvantages associated with their use. For example, guaiac-basedtests indicate only the presence of peroxidase and pseudoperoxidasecompounds, such as heme, that are present in a sample. Consequently,these tests are not specific for human blood, and are therefore subjectto false-positive results if the patient's stool is contaminated withcross-reacting compounds. Such cross-reacting compounds include, forexample, non-human blood breakdown products from under-cooked meat,certain vegetable products, and some drugs. According to currentlyaccepted medical practice, a patient demonstrating a positive resultshould then undergo a flexible sigmoidoscopy or colonoscopy to identifythe source of the bleeding in the colon or rectum. These procedures canbe invasive, medically complicated, and expensive. To minimize falsepositive reactions and the unnecessary follow-up procedures,guaiac-based FOB tests require a restrictive diet for up to three daysprior to testing.

Recent reports in the literature (Allison, et al. N. Eng. J. Med. 344:155-159 (1996); and Favennec et al., Annales de Biologie Clinique 50:311-313 (1992)) have suggested that screening by guaiac and confirmationof positive results by an immunological test, with absolute specificityfor human blood, would increase the value of FOB test results. By thismeans, only those patients with confirmed gastrointestinal bleedingwould be subjected to the expensive follow-up procedures, leading tosignificant savings in healthcare delivery cost and reducedinconvenience to the patient.

The present invention relates to a device which is useful for thedetection of any aqueous soluble or suspendable analyte which isdetectable either immunologically (e.g., an antigen or hapten), or basedon a chemical property associated with the analyte. Thus, with respectto FOB tests, the device of the present invention can be adapted toeither guaiac-based testing, or immunological testing. The preferredformat for immunological testing is immunochromatography. This format isdescribed generally in U.S. Pat. Nos. 5,591,645 and 5,622,871, thedisclosures of which are incorporated herein by reference.

Prior to discussing the invention in greater detail, a brief review ofthe immunochromatography process will be provided to establish certainprinciples. To detect an analyte of interest by immunochromatography,two binding reagents which bind specifically and non-competitively tothe analyte of interest may be employed. A first specific bindingreagent is labelled and is free to migrate. When introduced to a sampleto be tested for the presence of the analyte of interest, the firstspecific binding reagent binds to the analyte of interest, if present.The second specific binding reagent is immobilized in a detection zoneon a liquid-conductive solid phase material, the detection zone beingremote and downstream from the location of initial contact between thefirst binding reagent and the analyte of interest. A solvent frontcarrying the mobile first specific binding reagent complexed withanalyte of interest (if present) migrates along the liquid-conductivesolid phase material through the detection zone. If analyte is presentin the sample, the immobilized second specific binding reagent binds theanalyte thereby forming an immobilized sandwich complex comprising thefirst specific binding reagent (which is labelled), the analyte ofinterest, and the second specific binding reagent (which isimmobilized). Detection of the label immobilized in the detection zoneis indicative of the presence of analyte of interest in the sample. Inmost embodiments, the first and second specific binding reagents areeither polyclonal or monoclonal antibodies.

Preferred embodiments of the present invention are comprised of ahousing having a front panel and a rear panel; a sample applicationmatrix disposed between the front panel and the rear panel, the housingbeing adapted for application of the sample to the sample applicationmatrix; a testing element insertion window in the housing; and aninsertable testing element which, when inserted, communicates with thesample application matrix. In preferred embodiments, at least oneaperture is provided in the housing which is in direct communicationwith the sample application matrix. This aperture provides access to thesample application matrix for the purpose of applying sample. In otherembodiments, multiple apertures in the housing are provided for sampleapplication thereby facilitating, for example, the testing of samplescollected on multiple days in a single test.

The housing is preferably constructed of a flexible, creasable,water-resistant material. Examples of such material include coated paperor card stock, or thin plastic sheet stock. In preferred embodiments,the housing is constructed from a single sheet of stock which is foldedto create a plurality of panels or faces, including the front panel andthe rear panel. Alternatively, multiple webs may be laminated togetherto construct a similar structure.

The sample application matrix is disposed between the front and rearpanel and may be attached to either of the two panels with a non-solubleadhesive. The selection of a material for the sample application matrixis, to some degree, dependent upon the type of sample to be applied.Generally speaking, however, an open-celled, chemically inert matrix(e.g., porous plastic, filter paper, glass fiber) is preferred. Such anopen-celled matrix allows rapid and complete desiccation of the samplein situ. Rapid and complete desiccation minimizes the possibility ofsample breakdown due, for example, to microbial presence. Followingsample application, the testing device is returned to a physician ortesting laboratory for completion of the test process.

Given the description which follows, one of skill in the art willrecognize that the testing element may be provided in an array ofalternative embodiments. Referring to the immunochromatographicembodiment, for example, a required element of the test strip is aliquid-conductive solid phase material to which a detection reagent(described above as the second specific binding reagent) may beimmobilized. This solid phase material is preferably nitrocellulose.Nitrocellulose is a charged matrix to which an appropriately chargedreagent, such as a monoclonal antibody, may be immobilized without priorchemical treatment. Alternatives such as filter paper may also be used,however, chemical coupling (e.g., CNBr coupling) is required to attach acharged reagent such as an antibody to a matrix of this type.

A preferred liquid-conductive solid phase material is a nitrocellulosemembrane having a pore size of at least about 1 micron. Nitrocellulosemembranes best adapted for use in connection for immunochromatography ofthis type have a pore size of about 5-20 microns. The selection ofparticular pore size dictates flow rate. Depending upon the particularapplication, a faster or slower flow rate may be indicated and anappropriate solid phase material is selected.

To facilitate handling, it is desirable to provide a backing to thenitrocellulose membrane. A thin plastic sheet stock (e.g., lexan orpolystyrene) may be cut to provide a suitable water resistant backingfor the solid support. Such sheet stock is selected so as not tointerfere with the reading of a test result. For example, the selectionof a white or clear sheet stock is generally preferred. In analternative embodiment, the liquid-conductive solid phase material maybe sandwiched between such water resistant sheet stock.

When inserted into the housing, the test element is designed tocommunicate with the sample application matrix. Although thiscommunication may be direct between the sample application matrix andthe liquid-conductive solid support, in a preferred immunochromatographyembodiment, additional elements are incorporated. For example, aconjugate pad may be provided. In use, the conjugate pad is disposedbetween the sample application matrix and the liquid-conductive solidsupport of the testing element. As will be discussed in greater detailbelow, the conjugate pad provides a matrix for the deposition of alabelled detection reagent which is free to migrate when rehydrated (thefirst specific binding reagent in the brief review ofimmunochromatography provided above). The sample is desiccated withinthe sample application matrix prior to the insertion of the testingelement. At the time of rehydration during the testing step, thelabelled detection reagent within the conjugate pad is also resuspendedand resolubilized. If analyte is present in the sample, the labelledreagent binds to the analyte and the complex is carried along with thesolvent front to the detection zone of the testing element. While theconjugate pad may communicate directly with both the liquid-conductivesolid support and the sample application matrix, additional elements maybe incorporated as discussed in the Description of Preferred Embodimentssection which follows.

At the end of the testing element distal to the sample applicationmatrix when in use, an optional absorbent pad is attached, incommunication with the liquid-conductive solid phase material. This padprovides a solvent sink which drives the migration of the liquid samplethrough the detection zone. It is important that the absorbent pad havesufficient volume to drive the migration to the extent thatsubstantially all unbound labelled detection reagent is carried beyondthe detection zone of the testing element. One of skill in the art willrecognize that an absorbent pad is a non-essential element. The need forthis element can be obviated, for example, by extending the length ofthe liquid-conductive solid phase material beyond the detection zonesuch that a sufficient volume is carried through the detection zone.

In use, a sample is applied to the sample application matrix, preferablythrough an aperture in the housing which is in direct communication withsaid matrix. The sample is applied to the sample application matrix in aconventional manner. For example, a fecal smear may be applied to thesample application matrix. Alternatively, toilet bowl water may besampled using an absorbent swab. In the latter sampling method, a shorttime may be allowed for hemoglobin to diffuse from the stool prior tosampling, or the swab may be used to disperse the stool into the toiletbowl water. The swab is then used to sample the water and transfer it bytouching or “painting” the sample collection matrix. The liquid sampletransferred is typically nearly colorless.

Depending upon the nature of the analyte, the testing device with sampleapplied may be stored in this form for a period of days, weeks or monthsprior to testing. To determine the presence of an analyte, the sample isrehydrated by adding an appropriate solution to the sample applicationmatrix. The solution can be added through the same housing aperture(s)through which sample was applied. However, in most instances it ispreferable to provide a second aperture, or aperture series, in thehousing through which solvent is applied. This second aperture, oraperture series, is also in communication with the sample applicationmatrix. Preferably, solvent applied through a solvent applicationaperture must migrate through the region of the sample applicationmatrix where sample was actually applied, prior to reaching the point onthe sample application matrix which communicates with the testingelement.

The labelled detection reagent may be introduced into theimmunochromatography assay in a variety of ways. For example, thelabelled detection reagent may be solubilized in the solution used torehydrate the contents of the sample application matrix prior to theresolubilization of the sample components. Alternatively, as discussedabove, the labelled detection reagent may be introduced in solution intothe conjugate pad and desiccated in situ. In this embodiment, thelabelled detection reagent is resolubilized as the resolubilizationsolution migrates from the sample application matrix to the testingelement. In yet another embodiment, a solution containing the labelleddetection reagent may be added to the sample application matrix prior tothe application of the sample. This solution is then desiccated in situ.In this embodiment, analyte of interest, if present, and labelleddetection reagent will be solubilized from the dry sample applicationmatrix at the time of testing.

Of the embodiments described in the preceding paragraph, the use of aconjugate pad is preferred for most embodiments. The addition of thelabelled detection reagent to the resolubilization solution prior tosample resolubilization has the disadvantage of using the expensivedetection reagent (which could require storage at 4° C.) in aninefficient manner. With respect to the desiccation in situ of thelabelled detection reagent in the sample application pad prior to sampleapplication, this would result in the establishment of a test device inwhich the housing element is dedicated to a particular assay. One of themany benefits of the disclosed device is the fact that the housing(together with other elements of the device excluding the testingelement) is totally generic. Thus, the test housing component of thetesting device can be purchased in bulk and stored as needed for any ofa variety of testing requirements. The relatively expensivetest-specific component is the testing element which can be selected fora particular need and used in conjunction with the generic housing.

Preferably the labelled detection reagent is a monoclonal or polyclonalantibody specific for a first epitope of the analyte of interest,coupled to a detectable label. The detectable label can be coupled tothe antibody by any of the applicable techniques known in the artincluding, for example, covalent bonding and passive adsorption;

The detectable label may be a direct or an indirect label. A directlabel is a label which is readily visible in its natural state, eitherto the naked eye, or with the aid of optical devices. A label which isvisible only in the presence of external stimulation, such asultraviolet light, is also considered to be a direct label. Examples ofdirect labels include dye sols (e.g., colloidal carbon), metallic sols(e.g., gold and iron), fluorescent particles and colored latexparticles.

Indirect labels require the addition of one or more developing reagents,such as substrates, to facilitate detection. Such labels include, forexample, enzymes such as alkaline phosphatase and horseradishperoxidase.

The immobilized capture reagent is also typically a monoclonal orpolyclonal antibody which is specific for a second epitope or range ofepitopes on the analyte of interest. Thus, analyte present in thesample, whether bound by the detection reagent or not, is bound by theimmobilized binding reagent in the detection zone. In a case in which adirect label is employed, a visible line appears on theliquid-conductive solid support as bound label accumulates in thedetection zone. The appearance of this line may be diagnostic for thepresence of analyte of interest in the sample.

An optional control zone can also be integrated into the testingelement. The function of a control zone is to convey an unrelated signalto the user which indicates only that the testing process is completeand that the binding interaction which results in the detectableunrelated signal has taken place as expected. For example, the controlzone may comprise an “anti-mouse” polyclonal antibody immobilized to theliquid-conductive solid phase material, preferably downstream of thedetection zone. Assuming that the detection reagent is a murinemonoclonal antibody linked to a detectable label, detection reagents notbound in the detection zone through a sandwich interaction involving theanalyte of interest will ultimately bind in the control zone. In theabsence of a signal in the detection zone, a control zone signal wouldindicate to the user that, for example, the sample contained nothingthat resulted in general interference with an immunological assay. Itcan be imagined, for example, that extremes of pH or salt concentrationcould result in general interference through conformational changes orphysical destruction on one or more of the participants in theimmunologically based interaction to be detected. The inclusion of acontrol zone functions to provide a degree of-confidence with respect tosuch variables.

The analyte of interest is determined in advance to be one which isdiagnostic of a particular condition. For example, in connection withFOB tests, the analyte of interest is preferably human hemoglobin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are perspective views from the front of the device of thepresent invention.

FIGS. 2A-2B are perspective views from the rear of the device of thepresent invention.

FIG. 3 is an exploded cross-sectional view of the testing element of thepresent invention.

FIG. 4 is a cross-sectional view of-the device of the present inventionas taken along line 4—4 in FIG. 2B.

FIG. 5 is a top view of the device of the present invention as shown inpre-folded form.

DESCRIPTION OF PREFERRED EMBODIMENTS

By way of example only, certain preferred embodiments of the inventionwill now be described in detail with reference to the accompanyingdrawings.

Referring to FIG. 1, the testing device of the present invention isshown as configured for the detection of fecal occult blood in stool byimmunochromatographic methods. FIG. 1A shows the device of the presentinvention with a front panel cover (10) comprising two sampleapplication cover flaps (11 and 13) in the closed position. By raisingflap (11), a patient exposes a first sample application aperture (14) inthe front panel (17) of the device (FIG. 1B). The first sampleapplication aperture is in communication with a sample applicationmatrix (18) (shown in FIG. 4). Sample is applied to the sampleapplication matrix (18) via the sample application aperture (14).Following application of the sample, cover flap (11) is closed andsealed. A pressure sensitive adhesive with a removable backing strip(19) is provided for this purpose. The process is then repeated on asecond consecutive day and sample is applied via the sample applicationaperture located behind flap (13). While the embodiment shown in FIGS.1A and 1B has only two sample application apertures, this is intended tobe non-limiting. The sealed testing device is then forwarded to adoctor's office or testing laboratory for determination of test results.

Upon receipt, a technician at the doctor's office or testing laboratoryopens the testing window (25) located on the rear panel cover (23), asshown in FIG. 2A. Perforations are provided for the opening or removalof the testing window to facilitate access. Opening or removal of thetesting window (25) reveals several apertures which characterize therear panel (16). These include solvent application apertures (27 and 29)and testing element insertion aperture (31). A testing element (33) isthen inserted into the testing element insertion aperture (31). Thetesting element (33) contains a reagent enabling the detection of theanalyte of interest in the sample.

The testing element is shown in exploded cross-section in FIG. 3. Thetesting element is comprised of a liquid-conductive solid phase material(35) which is preferably nitrocellulose membrane. To facilitatehandling, a backing sheet (39) is provided. Non-absorbent plastics suchas lexan or polystyrene are preferred backing sheet materials. Preferredembodiments also include one or more layers of high capacity liquidconducting material referred to herein as “bridging layers”. A bridginglayer (38) is shown in FIG. 3. In the embodiment of FIG. 3, a conjugatepad (37) is disposed between bridging layer (38) and theliquid-conductive solid phase material (35). As discussed above inconnection with preferred immunochromatographic embodiments, theconjugate pad contains labelled detection reagent desiccated in situ. Anabsorbent pad (41) is also provided as a component of testing element(33). The absorbent pad (41) functions as a solvent sink thereby drivingthe migration of the solvent front. The elements shown in FIG. 3 areassembled using a non-water soluble adhesive. It will be evident thatthe overlap of elements such as bridging layer (38) and conjugate pad(37) creates a progressive wedging effect which results in good liquidconductive contact between the sample application matrix (18) and thetesting element (33), following insertion of the testing element (33)into the testing element insertion aperture (31). Immobilized capturereagent is attached to the liquid-conductive solid phase materialthereby creating a detection zone (43) on testing element (33).

FIG. 4 is a cross-section of the device with the testing element (33)inserted. FIG. 4 shows many of the previously discussed elementsincluding, for example, testing element (33) and individual componentsthereof (absorbent pad (41), liquid-conductive solid phase material(35), conjugate pad (37), bridging layer (38) and backing sheet (39));sample application cover flap (13); front panel (17) with sampleapplication aperture (15); rear panel (16); rear panel cover (23) withtesting window (25); and sample application matrix (18). Also shown isan optional element not previously discussed. This optional element isreferred to as a spacer panel (42). The spacer panel, which is shown ingreater detail in FIG. 5, functions to create a testing elementinsertion void space between the sample application matrix (18) and thefront panel (17) in the assembled device. Spacer panel (42) includes asecond testing element insertion aperture (44) and embossed point (48),also shown in FIG. 5. As shown in FIG. 4, when testing element (33) isinserted, it occupies this testing element insertion void space. Theprogressive wedging referred to previously in connection with FIG. 3results in good liquid-conductive contact between the sample applicationmatrix (18) and the testing element (33).

Again referring to FIG. 4, following insertion of the testing element,the technician rehydrates the sample by adding a solvent to the sampleapplication matrix (18) via solvent aperture (29) in rear panel (16).The solvent solubilizes sample components in the sample applicationmatrix (18) and carries the solubilized components through bridginglayer (38) and into the conjugate pad (37) with the solvent front. Inthe conjugate pad (37), labelled detection reagent is solubilized andbinds to analyte if present in the sample. The solvent front, and anysoluble materials carried with the solvent front, then move on to theliquid-conductive solid phase material (35). If analyte is present inthe sample, a visibly detectable complex comprising analyte, labelleddetection reagent and immobilized capture reagent forms in detectionzone (43).

In a preferred embodiment, front panel cover (10), rear panel cover(23), front panel (17), rear panel (16) and spacer panel (42) areproduced from a single sheet of stock by appropriate cutting andfolding. Referring to FIG. 5, a generally rectangular sheet of stock isprovided. Solvent application apertures (27 and 29) and a testingelement insertion aperture (31) are cut in rear panel (16). Sampleapplication apertures (14 and 15) are cut in front panel (17). Theoutline of the diagnostic window (25) is perforated in the rear panelcover (23). The front panel cover (10) is cut to form two flaps (11 and13) which will seal the sample application apertures following sampleapplication. Pressure sensitive adhesive (19) is provided for sealingsample application cover flaps (11 and 13). Spacer panel (42) is cut toprovide a second testing element insertion aperture (44). In addition,the spacer panel (42) is optionally embossed at embossed points (46 and48). As an alternative to embossed points (46 and 48), optional spacerelements may be attached to spacer panel (42) using an adhesive. Thefunction of the optional embossed points (46 and 48) or the alternativeoptional spacer elements, is to increase the testing element insertionvoid space between the sample application matrix (18) and the frontpanel (17) in the assembled device, if desirable. Whether or not toinclude such optional elements depends, for example, on the relativethicknesses of the sample application matrix (18) and the stock fromwhich the housing is produced. Folds are made along lines D—D, C—C, B—B,and A—A to form the housing. Prior to folding, the sample applicationmatrix is appropriately positioned and adhesive is applied inappropriate locations to aid in maintaining the relationship of elementsin the folded housing.

Exemplification

Construction of Testing Device

Test elements were manufactured by laminating the following componentsto a white plastic support (high impact polystyrene, 0.5 mm), coated onone surface with adhesive (3M, St. Paul, Minn., #465 transfer tape), asshown in FIG. 3:

1) nitrocellulose membrane (Millipore, Bedford, Mass., Type STHF0200, 18mm) striped with monoclonal anti-human hemoglobin antibody at 2 mg/ml;

2) absorbent for absorbent pad (Ahlstrom, Mt. Holly Spring, Pa., Grade904, 18 mm);

3) conjugate pad (General Polymeric, Reading, Pa., 25 micron UHMWPEskived tape, 10 mm) infiltrated and dried in situ with polyclonalanti-human hemoglobin antibody conjugated to colloidal gold (EYLaboratories, San Mateo, Calif.); and

4) conductive paper for bridging layer (Ahlstrom, Grade 1281).

Following lamination, the web was slit at 6 mm intervals to formindividual test elements.

Housings (73 mm×76.2 mm), as depicted in FIG. 5, were manufactured fromwaterproofed (polycoated) SBS cardboard. The sample application matrix(Porex, Fairburn, Ga., HDPE Type 4588) was applied to the rear panel ofthe housing with transfer adhesive (3M, #465).

EXAMPLE 1

Human blood was diluted 1:10,000 and 1:100,000 in distilled water. Foreach of the dilutions of blood, and for a control sample of distilledwater, 25 μl was added to each of the two sample application aperturesof a testing device and allowed to air dry for two hours. 100 μlreconstituting reagent (P.B.S. containing 0.5% Bovine Serum Albumin, 1%Triton X100 and 0.1% sodium azide) was added to each solvent applicationaperture and a test strip inserted. A clear red line developed on thetest strip with the two blood dilutions, i.e. positive detection,whereas the water sample gave no detectable signal (i.e. a negativeresult).

In an otherwise identical experiment, the same blood dilutions wereadded (25 μl for each) to Hemoccult (SmithKline Diagnostics, Palo Alto,Calif.) slides and a ColoCare (Helena Laboratories, Beaumont, Tex.) testpad (a device for detecting blood in the toilet bowl water that is addeddirectly to the toilet bowl).

Results 10⁻⁴ 10⁻⁵ Water Hemoccult + − − ColoCare + − − Device of + + −Present Invention

EXAMPLE 2

Fresh human blood (50 μl) was added to the water in a toilet bowl (˜2L). After full dispersion of the added blood, the water was sampled witha dacron swab (Hardwood products, Guildford, Me.) and transferred to aHemoccult card and a to the sample application matrix of the device ofthe present invention. Following the sampling, a ColoCare pad was addedto the toilet bowl and observed for any change in color.

Results

The device of the present invention readily detected the blood, whereaswater taken from the bowl before the addition of the blood testednegative. The Hemoccult and ColoCare tests remained clearly negativewith the water to which the blood had been added.

What is claimed is:
 1. A testing device for the identification of ananalyte of interest, comprising: a) a housing having a sampleapplication matrix for: i) receipt of a liquid-containing sample; ii)desiccation of the liquid-containing sample in situ; iii) rehydration ofthe desiccated liquid-containing sample for transfer to a testingelement; and iv) a testing element aperture in the housing to receive atesting element inserted therein and hold said testing element in directliquid-conductive communication with the sample application matrix; andb) an insertable testing element which, on insertion into the testingelement aperture in the housing, is retained within the housing indirect liquid-conductive communication with the sample applicationmatrix such that upon rehydration, resolubilized or resuspendedcomponents of the liquid-containing sample are carried from the sampleapplication matrix to the testing element.
 2. The testing device ofclaim 1 wherein the analyte of interest is an antigen or hapten.
 3. Thetesting device of claim 2 wherein the antigen or hapten is a diagnosticindicator of a disease state in an organism.
 4. The testing device ofclaim 3 wherein the organism is a human.
 5. The testing device of claim4 wherein the disease state is selected from the group consisting ofcancer and pathogenic infection.
 6. The testing device of claim 2wherein the antigen or hapten is a contaminant in food or water.
 7. Thetesting device of claim 6 wherein the antigen or hapten is associatedwith a disease state in an organism.
 8. The testing device of claim 7wherein the organism is a human.
 9. A testing device for theidentification of an analyte of interest, comprising: a) a housinghaving i) a front panel having at least one sample application aperturetherein; ii) a rear panel having at least one solvent applicationaperture therein; iii) a sample application matrix disposed between therear panel and the front panel, the sample application matrix being incommunication with the sample and solvent application apertures of thefront and rear panels; and (iv) a testing element aperture in thehousing to receive a testing element inserted therein and hold saidtesting element in direct liquid-conductive communication with thesample application matrix; and b) an insertable testing elementcontaining a reagent enabling detection of the analyte of interest, andwhich, on insertion into the testing element aperture in the housing, isretained within the housing in direct liquid-conductive communicationwith the sample application matrix.
 10. The testing device of claim 9further comprising a front panel cover and a rear panel cover which,when closed, restrict access to the sample application aperture and thesolvent application aperture.
 11. The testing device of claim 10 furthercomprising a spacer panel disposed between the front panel and the rearpanel, said spacer panel being designed to create a testing elementinsertion void space between the sample application matrix and the frontpanel in the assembled device.
 12. The testing device of claim 9 whereinthe analyte of interest is an antigen or hapten.
 13. The testing deviceof claim 12 wherein the antigen or hapten is a diagnostic indicator of adisease state in an organism.
 14. The testing device of claim 13 whereinthe organism is a human.
 15. The testing device of claim 14 wherein thedisease state is selected from the group consisting of cancer andpathogenic infection.
 16. The testing device of claim 15 wherein thedisease state is characterized by occult gastrointestinal bleeding. 17.The testing device of claim 16 wherein the analyte of interest ishemoglobin, or a fragment thereof.
 18. The testing device of claim 9wherein the insertable test strip is an immunochromatographic teststrip.
 19. The testing device of claim 18 wherein theimmunochromatographic test strip comprises a liquid-conductive solidphase material affixed to a backing material.
 20. The testing device ofclaim 19 wherein the insertable immunochromatographic test strip iscomprised of a contact zone which, following insertion, contacts thesample collection matrix and conducts a solvent front from the samplecollection matrix through a detection zone which contains a specificbinding reagent, the detection zone being spatially distinct from thecontact zone.
 21. The testing device of claim 16 wherein the sampleapplied to the sample collection aperture is fecal material.
 22. Thetesting device of claim 16 wherein the fecal material is obtained bysampling toilet bowl water.
 23. The testing device of claim 11 whereinthe specific binding reagent in the detection zone is an antibodyspecific for a human blood component.
 24. The testing device of claim 23wherein the human blood component is hemoglobin or a fragment thereof.